CVE-2026-3611

Description

The Honeywell IQ4x building management controller, exposes its full web-based HMI without authentication in its factory-default configuration. With no user module configured, security is disabled by design and the system operates under a System Guest (level 100) context, granting read/write privileges to any party able to reach the HTTP interface. Authentication controls are only enforced after a web user is created via U.htm, which dynamically enables the user module. Because this function is accessible prior to authentication, a remote user can create a new account with administrative read/write permissions enabling the user module and imposing authentication under attacker-controlled credentials. This action can effectively lock legitimate operators out of local and web-based configuration and administration.

PUBLISHED Reserved 2026-03-05 | Published 2026-03-12 | Updated 2026-03-12 | Assigner icscert

Problem types

CWE-306 Missing authentication for critical function

Product status

Credits

Gjoko Krstic of Zero Science reported this vulnerability to Honeywell. finder

References

www.cisa.gov/news-events/ics-advisories/icsa-26-069-03

github.com/...p/csaf_files/OT/white/2026/icsa-26-069-03.json

www.honeywell.com/us/en/contact

cve.org (CVE-2026-3611)

nvd.nist.gov (CVE-2026-3611)

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